The proposed project, titled "Study of High-Risk Drug Use Settings for HIV Prevention," is an ethnographic study of shooting galleries, crack houses, and base houses in Hartford, CT, designed to document the nature, structures, social relations, and natural history of these sites, as well as the dynamics of site users' social networks, in order to determine the potential for HIV prevention interventions in these locations. The investigators also will analyze personal networks of high-risk site users to assess whether and to what extent the benefits of social level interventions diffuse through site users to sex partners and other drug users who do not frequent high-risk sites. Specific aims are to; 1) document the range of variation in structures, social relations and natural histories of high-risk drug use settings in targeted neighborhoods; 2) describe and analyze the properties of high-risk site users' personal risk networks, including changes in shared risk and preventive behaviors, network density and stability, and changing pathways for diffusion of HIV-risk or prevention effectors; 3) assess the receptivity of high-risk site gatekeepers (e.g., housemen) and site users to on-site prevention efforts; and 4) assess the potential for diffusion of benefits of a social level intervention for risk reduction beyond high- risk settings. A total of 16 high-risk sites (eight shooting galleries; eight crack/base houses) will be identified and "recruited" for a long- term (2 year) ethnographic study, from which the investigators will draw an index sample of 128 site users for interviewing on HIV risk, high-risk site use, network characteristics, and recognition/use of social level intervention materials/information. Index individuals will identify and help recruit 384 non-site-using risk network members to receive the same set of instruments. Both index and network participants will be interviewed three times at 6-month intervals with the same measures. Quantitative and qualitative data from ethnographic observations and interviewing and network surveys will be triangulated for exploratory analyses and hypothesis generation regarding site and risk network stability and change, and for development of transition probability matrices and other statistical models. A manualized intervention will result from these analyses for testing in a subsequent study.